An examination of digital equipment recovered from the home of the couple who killed 14 people in San Bernardino last week has led FBI investigators to believe the shooters were planning an even larger assault, according to federal government sources.

Investigators on Thursday continued to search for digital footprints left by Syed Rizwan Farook and Tashfeen Malik, scouring a downtown San Bernardino lake for electronic items, including a hard drive that the couple was hoping to destroy, sources told The Times.

FBI agents will probably spend days searching Seccombe Lake and canvassing the neighborhood for clues after receiving a tip that the couple may have visited the area on the day of the attack, according to David Bowdich, assistant special agent in charge of the FBI's Los Angeles field office.

Farook and Malik were in the final planning stages of an assault on a location or building that housed a lot more people than the Inland Regional Center, possibly a nearby school or college, according to federal sources familiar with the widening investigation.

Memorial to the San Bernardino massacre victims grows

Luis Sinco / Los Angeles Times

A memorial to victims of the terrorist attack in San Bernardino continues to grow near the Inland Regional Center.

A memorial to victims of the terrorist attack in San Bernardino continues to grow near the Inland Regional Center. (Luis Sinco / Los Angeles Times)

Investigators have based that conclusion on evidence left behind on Farook and Malik's computers and digital devices, not all of which the couple were able to destroy before they were killed in a firefight with police, the sources said.

Images of San Bernardino-area schools were found on a cellphone belonging to Farook, according to a law enforcement source. But the source cautioned that Farook may have had a legitimate reason to have the images because his work as a county health inspector involved checking on school dining facilities.

On Thursday, one of the federal government sources told The Times that Farook asked his friend and neighbor, Enrique Marquez, to buy two military-style rifles used in the attacks because he feared he "wouldn't pass a background check" if he attempted to acquire the weapons on his own. The rifles were bought at a local gun store, the source said.

Farook was self-radicalizing around that time, FBI Director James Comey said, and met Malik soon after, eventually escorting her to the United States. Farook was a practicing Muslim. Marquez converted to Islam around the time he purchased the weapons, sources have told The Times.

FBI agents believe Farook abandoned his plans to launch the earlier attack after a law enforcement task force arrested three men in Chino in November 2012. The men were later convicted of charges related to providing material support to terrorists and plotting to kill Americans in Afghanistan. A fourth man arrested in Afghanistan also was convicted in the scheme.

Bowdich said federal agents are investigating whether the men had ties to Farook.

Marquez has emerged as a central figure in the investigation. The FBI had been conducting interviews with 24-year-old, who checked himself into a mental health facility after the attacks.

The former Wal-Mart security guard has waived his Miranda rights and cooperated with the inquiry, and it was Marquez who told FBI agents about Farook's earlier plans, according to one of the government sources, who also requested anonymity.

(Rick Loomis / Los Angeles Times)

"They were talking generally about something, but I don't think it made it to anything specific," one of the sources said of the earlier plot. "I don't think it got to a time or a place."

The source said it remains unclear whether Marquez had any involvement in the planning of the shooting or had any prior knowledge that an attack was pending.

Marquez, a cycling enthusiast who wanted to join the U.S. Navy, was a longtime friend and neighbor of Farook. He also married the sister of Farook's sister-in-law last year, although the circumstances of the union are now under investigation, a government official previously told The Times.

There was no paperwork transferring ownership of the assault rifles from Marquez to Farook, as required by California law, government officials told The Times.

Hours after the shooting, Marquez posted a cryptic message on his Facebook page.

"I'm. Very sorry sguys," the message read. "It was a pleasure."

Bowdich on Thursday declined to answer questions about Marquez, who has not been charged with a crime.

Marquez told FBI agents that the Facebook post has been "misunderstood," according to one of the government sources. Agents are concerned that Marquez's mental and emotional state may affect what he has been telling interrogators, the source said.

While Marquez has spoken to agents about his ties to Farook, federal officials are still working to verify the information he has provided, the source said.

Marquez's mother, Armida Chacon, addressed reporters on Thursday from her Tomlinson Avenue home in Riverside, sobbing as she said she hadn't been in contact with her son since the day of the massacre.

"I don't know how this happened.... My world is upside-down," she said. "My life changed Wednesday."

Chacon was outside with one of her sons, cleaning up the broken glass and twisted panels of their garage door. The damage occurred when federal agents raided the stucco home over the weekend.

As she combed through the wreckage of the garage door, Chacon eventually turned to the reporters camped out on the street and agreed to an off-camera interview.

Marquez was his mother's "right hand at home," helping take care of his brothers, she said.

She said her son loved to hang out with friends and go to parties.

"My son is a good person," she said.

When asked about Farook, Chacon said her son was friends with him and "nothing more."

Chacon said she was overwhelmed by news of the shooting and had spent the last several days crying inside her home.

A version of this article appeared in print on December 11, 2015, in the News section of the Los Angeles Times with the headline "Divers search lake for killers' secrets - Investigators tracing couple's digital footprints believe they were planning a bigger attack." —
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